The present invention relates to a chain tensioner for use with an automotive cam drive assembly.
Chain tensioners are often employed to maintain a certain degree of chain tautness to reduce rattle noise associated with a slack chain in automotive applications such as drive and timing chains. In an internal combustion engine with an in-block camshaft, a cam drive assembly includes a crankshaft sprocket driving a camshaft sprocket via a timing chain. The cam drive is housed within a vertical cam drive cavity in the engine block. During engine operation, dynamic forces in the cam drive induce variations in chain tension, thereby necessitating a chain tensioner. The chain tensioner is typically mounted to a base plate or bracket which is bolted to the engine block. Therefore the engine block must include pre-drilled, pre-cast, or pre-formed holes to receive the mounting bolts. In some instances, this mounting scheme may be undesirable. For example, if a tensioner is to be retrofit to the engine after the engine has been designed and assembled, then drilling mounting holes in the block would be prohibited. Further, mounting bolts and brackets add piece cost and assembly cost to the design.
The need exists for a chain tensioner, packagable in a cam drive cavity, without the need for costly tensioner-specific fastening means.
The present invention is directed to a chain tensioner to be used in an automotive engine where the tensioner is retained by complementary geometrical features on the tensioner and the supporting structure of the engine. The geometrical features function to retain the tensioner in position without the need for mounting bolts and brackets, thereby reducing cost and mass. Additionally, this way of retaining the tensioner within an engine allows an engine to be later retrofit with a tensioner if desired without modification to the engine block itself.
The chain tensioner is comprised of a stationary portion and a flexible spring portion supported therewith and having a nylon shoe fixed to the flexible spring portion to provide a contact tension surface for the chain. The stationary portion includes a geometrical interlocking feature to mate with a complementary feature in the supporting engine block structure.
The tensioner, which is held in place by the engine geometry, may be located for assembly by existing fastener bolts which are already in the engine to mount another component and therefore may serve the dual function of locating the tensioner and fastening the other component to the engine.